ACT8810
Active- Semi
Rev 4, 01-Oct-09
ActivePathTM CHARGER
FUNCTIONAL DESCRIPTION CONT’D
two current-limited nSTAT outputs that can directly
drive LED indicators or provide a logic-level status
When ACIN is driven to a logic-low, the ActivePath
circuitry operates in “USB-Mode”, which enforces a
maximum charge current setting of 500mA, if
CHGLEV is driven to a logic-high, or 100mA, if
CHGLEV is driven to a logic-low.
signal to the host microprocessor.
Dynamic Charge Current Control (DCCC)
The ACT8810's charge current settings are
summarized in the table below:
The ACT8810's ActivePath charger features
Dynamic Charge Current Control (DCCC) circuitry,
which continuously monitors the input supply and
prevents input overload conditions by dynamically
adjusting the charge current to keep the input voltage
from dropping below the DCCC voltage threshold.
Table 19:
ACIN and CHGLEV Inputs Table
CHARGE
CURRENT
ICHG (mA)
PRECONDITION
CHARGE CURRENT
ICHG (mA)
ACIN CHGLEV
By default, the DCCC voltage threshold is set to
4.4V, but it may also be programmed by connecting
a resistor from DCCC to GA, where the resistor has
value given by the following equation:
90mA or ISET
(Smallest one)
90mA or 12%ISET
(Smallest one)
0
0
0
1
VDCCC = 2 × (IDCCC × RDCCC
)
(2)
450mA or ISET
(Smallest one)
12% × ISET
Where RDCCC is the value of the external resistor,
and IDCCC is the value of the current sourced from
DCCC, typically 100μA.
1
1
0
1
50% × ISET
ISET
12% × ISET
12% × ISET
Charger Current Programming
Note that the actual charging current may be limited
to a current that is lower than the programmed fast
charge current due to the ACT8810’s internal
thermal regulation loop. See the Thermal
Regulation and Protection section for more
information.
The ACT8810's ActivePath charger features a
flexible charge current-programming scheme that
combines the convenience of internal charge
current programming with the flexibility of resistor
based charge current programming. Current limits
and charge current programming are managed as a
function of the ACIN and CHGLEV pins, in
combination with RISET, the resistance connected to
the ISET pin.
Battery Temperature Monitoring
The ACT8810 continuously monitors the
temperature of the battery pack by sensing the
resistance of its thermistor, and suspends charging
if the temperature of the battery pack exceeds the
safety limits.
ACIN and CHGLEV Inputs
ACIN is a logic input that configures the current-limit
of ActivePath's linear regulator as well as that of the
battery charger. ACIN features a precise 1.25V
logic threshold, so that the input voltage detection
threshold may be adjusted with a simple resistive
voltage divider. This input also allows a simple, low-
cost dual-input charger switch to be implemented
with just a few, low-cost components.
In a typical application, shown in Figure 11, the TH
pin is connected to the battery pack's thermistor
input. The ACT8810 injects a 100µA current out of the
TH pin into the thermistor, so that the thermistor
resistance is monitored by comparing the voltage at
TH to the internal VTHH and VTHL thresholds of 0.5V
and 2.5V, respectively. When VTH > VTHL or VTH < VTHH
charging and the charge timers are suspended. When
VTH returns to the normal range, charging and the
charge timers resume.
When ACIN is driven to a logic high, the ActivePath
operates in “AC-Mode” and the charger charges at
the current programmed by RISET
,
ICHG = 1V/RISET × KISET
(3)
The net resistance from TH to G required to cross
the threshold is given by:
where KISET = 640 when CHGLEV is driven to a
logic high, and K = 320 when CHGLEV is driven to
a logic low.
100µA × RNOM × kHOT = 0.5V → RNOM × kHOT = 5kꢀ
100µA × RNOM × kCOLD = 2.5V → RNOM × kCOLD = 25kꢀ
Innovative PowerTM
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Copyright © 2009 Active-Semi, Inc.
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